In far field imaging systems, such as telescopes, it is desirable to have diffraction limited lenses (i.e., devoid of aberrations) with very large apertures. It is well known that the resolution achievable with a diffraction limited lens is inversely proportional to the size of its aperture. Thus, larger lenses, which have larger apertures, produce finer resolution. Large optical lenses, however, are generally limited by their great weight and cost.
One method of avoiding large, high quality, expensive lenses is the use of an array of smaller, lower quality lenses. the use of an array of lenses increases the cross sectional area, and therefore the resolution of the system, but it also increases the aberration that must be corrected. Furthermore, the combination of multiple optical images at a common plane generates problems of angular resolution, piston error resulting from different lens distances from the object plane, and tilt error resulting from different lens angles. In previous optical imaging systems, the superposition of many individually produced images has not achieved the high resolution desired, especially at the small energy levels normally received. Thus, it has not been considered practical to use multiple apertures or synthetic imaging in most optical systems.
A need has therefore been recognized for an optical imaging system that employs multiple and/or synthetic aperture techniques to improve the resolution of low cost lenses. Furthermore, it is highly desirable that such a system provide automatic compensation for the optical errors inherent in a multiple or synthetic aperture system.